This application claims the priority of German Application No. 100 41 892.9 filed Aug. 25, 2000, which is incorporated herein by reference.
This invention relates to a method of directly determining setting values for the application point of regulation in a regulated draw frame for slivers. The control system of the draw frame in which the extent of draft of the sliver may be set has at least one preliminary control system for changing the draft of the sliver. Based on the drafted sliver, a number of quality-characterizing measured values, such as CV values may be sensed and utilized for formulating a function whose minimum represents an optimum application point of regulation for the control of the draw frame. The optimized application point of regulation may be determined in a pre-operational test run or a setting run of the draw frame.
The application point of regulation is an important setting magnitude in a draw frame to produce slivers with a high sliver uniformity, that is, with a small CV value.
In a known system, during a pre-operational setting run, the sliver is drafted between the mid rolls and the output rolls of the draw unit and is withdrawn by calender rolls which are adjoined by a measuring device for the CV value of the drafted sliver. In the pre-operational setting run a plurality of CV values are determined which represent a quality-characterizing magnitude for the drafted sliver. Based on such measured values, a function is formulated whose minimum value corresponds to a value which promises to be the best adaptation of the regulation actual sliver. The plurality of measured values which are plotted and based on which the function is formulated, are in each instance measured for a different setting value of the regulation. Thus, for the definition of the function to be evaluated, each incremental value of an incrementally changing parameter, for example, the application point of regulation of the xe2x80x9celectronic memoryxe2x80x9d, has to be associated with one of the measured values. For this purpose, on command, the control system sets, in the preliminary control system, an arbitrary, in most cases estimated, first value Rmin obtained from empirical values (for example, from a table) for the application point of regulation.
After passage of a certain sliver quantity which should be just as long that an unequivocal CV value may be calculated therefrom, a CV value designated Cv1 is maintained fixed. This measured value taken from the measuring device is applied to a memory of the control system. Thereafter the first set application point of regulation R of the preliminary control is changed by at least one incremental magnitude. Again, the sliver is allowed to run for a certain time period until a corresponding CV2 value is stored by the control system into the same memory range. In a similar manner a further incrementing of the application point of regulation is effected and a further measurement of a CV3 value takes place, until a number of values is available between a minimum application point of regulation Rmin and a maximum application point of regulation Rmax. The distances between two measured values are identical to obtain a displacement-constant scanning (uniform distance of the measured values). A secured, storage-ready value as a quality value for the function becomes available only when the measurement of the CV value has occurred in a sufficiently large number of individual measurements.
It is a disadvantage of the above-outlined system that the minimum value is determined by a time-consuming search. In this process, starting from Rmin one proceeds in small steps along the function curve until the Rmax value is reached. This involves a great number of measurements in small, incremental steps which is a complex procedure.
It is an object of the invention to provide an improved method of the above-outlined type from which the discussed disadvantages are eliminated and which in particular, ameliorates the determination and setting of the optimal application point of regulation at the regulating system of a draw unit and, more particularly, allows a more rapid determination of the application point of regulation. It is a further object of the invention to provide a method which also takes into consideration different, quality-characterizing magnitudes, such as different CV values.
These objects and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of directly determining setting values for an application point of regulation in a draw unit for drafting sliver includes the following steps: obtaining at least three measured values of a quality-characterizing magnitude, such as the CV value, of the drafted sliver; utilizing the measured values for formulating a function having a minimum constituting an optimal application point of regulation for controlling the draw unit; determining the optimal application point of regulation in a pre-operational run of the draw unit; and numerically computing a function between the quality-characterizing magnitudes and application points of regulation from the measured values.
The optimal application point of regulation (optimal dead period or delay) is determined by the draw frame itself by using the steps according to the invention. Based on the CV values of the sliver measured on line, the draw frame control system determines the optimal application point of regulation, that is, the machine optimizes itself. By the placement of as few as three measured values (Rmin, Rmax and an intermediate value Rx) it is feasible to rapidly calculate the minimum of the function and thus the optimized application point of regulation. By virtue of the fact that only few measured values need to be taken and suffice for the calculation, it is feasible in a simple manner to achieve a double time-reduction, that is, a more rapid determination of the optimized application point of regulation. The time saving further makes possible to take into consideration different, further quality-characterizing magnitudes whereby an even more accurate determination of the optimized application point of regulation is feasible.